Method of atomizing metal



Patented Feb. 8, 1949 METHOD or ATOMIZING METAL Gordon J. Le Brasse, AnnArbor, and Harold'E.

Francis, Detroit, Mich, assignors to'Federal- Mogul Corporation, De

tion of Michigan troit, Micha. corpora- Application February 6, 1946,Serial No. 645,947

2 Claims. (Cl. 18-473) This invention relates to a method of atomizinmetal and has for its principal object the provision of a method ofatomizing a metal alloy having as principal elements thereof, copper andlead, and by the practice of which method such alloy may be atomizedwithout the formation of an excessive coating of oxide on the particlesproduced thereby.

Objects of the invention include the provision of a method of atomizingan alloy having as principal elements thereof copper and lead, with orwithout the addition of tin, so as to form a loose mass of finelydivided particles, and by the practice of which the oxygen content ofthe mass of atomized particles, because of the oxide coating on theparticles produced during the atomization, does not exceed 0.5%; theprovision of a method of atomizing an alloy of the type above defined inwhich the alloy in" molten condition is subjected to the effects of highvelocity e water in a non-oxidizing or in a reducing atmosphere; theprovision of a method as above described in which the atomization of themetal is carried on in a closed space from which air has been displacedby a non-oxidizing or a reducing gas; the provision of a method as abovedescribed requiring the use of a minimum amount of a nonoxidizing or areducing atmosphere; the provision of a method as above describedincluding'the additional step' of effecting a separation offthe atomizedparticles 'in accordance with the size thereof; the provision of amethod as above described, including the use of means for dissipatingthe force of the stream of water after it has served its purpose inbreaking up the particles of molten metal being atomized; and theprovision of a method as above described by the practices of which metalof the character described may be quickly and economically atomized andin which the resulting particles of metal will have a minimum amount ofoxide coating" thereon.

The above, being among the objects of the present invention, the sameconsists in certain novel steps of operation to be hereinafter de:scribed with reference to the accompanying drawings, and then claimed,havingthe above and other objects in view.

'In .the accompanying drawings which illustrate a suitable form ofapparatus by means of which the method of the present invention may becarried out, and in which like numerals refer to like parts throughoutthe several different views;

Fig; 1 isa vertical sectional View taken centrally and longitudinallythrough a metalatomizing apparatus by'th-e use of which the method ofthe presentinvention may be carried out, 7

Fig. 2 is a vertical transverse sectional view takenon the line 22 ofFig. 1;

Fig; 3 is a vertical transverse sectional view taken on the line 3--3 ofFig. '1, and

"Fig. 4 is a fragmentary, vertical sectional view taken on the line 4 ofFig. 2.7

While the method of the present invention is believed of value in theatomization of any metal or metal alloygitis particularly useful intheproduction of the atomized metal disclosed and claimed in ourcopending application for Letters Patent of the United States forimprovement in Atomized metal, filed on evendate herewith, and seriallynumbered 645,948. The. apparatus herein shown as applicable tothe'carrying out of the present method formsthe subject matter of ourapplication 'for Letters Patent of 5 the United States for improvementsin Apparatus for atomizing metal, filed on even date herewith andserially numbered 645,946. The said copending applications dealparticularly with an atomized metal alloy in which copper and lead formessential elements and which particles have an oxide coating of adesirably'small'value, and to an apparatus for producing such atomizedparticles.

Atypical example of a copper-lead alloy in the atomizingof whichithepresent invention is particularly. adaptable is as follows:

' l 7 Per cent Lead 10to Nickel .0 to 2 Tin 0 to. 2 Phosphorus I 0 to0.10 Copper substantially the balance A typical example" of a leadbronze in the atomizing of which the present invention is particularlyadaptable is as follows:

' Per cent Lead 5 to' 30 Tin 5 to. 12 Zinc ()to' 6 Nickel 0 to '2Phosphorus 0 to 0.5 Copper substantially the balance the form of one ormore fine streams is discharged into a blast or spray of water simplydirected and surrounded by air. The blast of air breaks up the finestreams of molten metal into fine particles and solidifies them so thatthey produce a mass of loose powder-like material. However, the shorttime that such particles are exposed to the air in their molten state,as well as to the water, in accordance with conventional practices, issufficient to produce on each particle a coating consisting of one ormore of theoxides of lead. When tin is also an element of the alloy, atleast a part of the coating may consist of tin oxide. There are fivedifierent oxidesof lead, but in view of the temperatures involved it ispresumed likely that one or all of the following three lead oxides arepresent in such coating: PbO, Pb3O4 and PbzOa. Atomized particlesproduced in the conventional manner thus described will usually be foundto have an oxygen content, because of the oxide coating, in excess of-1%, probably averaging about 1.2%. The average oxygen content of thethree oxides above listed is 8.6%. If this average figure is used as abasis for calculating the amount of oxide present in a mass of theatomized alloy, then an atomized mass of the alloy having1% of oxygenwould mean that there would be about 11.6% lead oxide present. With anaverage oxygen content of 1. then there would be about 13.92% of leadoxide present in a mass of the atomized alloys under consideration. Thismeans that for a given amount of such atomized alloy, there is presentan average of in the neighborhood of 13% to 14% of the weight of themass in the form of an oxide coating on the particles.

Where a powder comprising such atomized particles of lead bearing copperalloys is applied as a coating to a steel strip and passed through asintering furnace to cause the various particles to adhere to oneanother and to the steel backing strip, as is a conventional practice inthe formation of bearings, the amount of oxide present in theconventionally formed powder is so great as to require reduction of theoxide coating in the sintering furnace, by the combined application ofheat and a reducing atmosphere, before a satisfactory bond can beobtained between the various particles and between the particles and thesteel strip. As a result, the passage of such strip through a sinteringfurnace has been considerably slowed down as compared to the speed thatwould be possible of such oxide coating were initially of no greatervalue than that at which satisfactory sintering may be produced by heatalone withoutthe necessity of reducing the percentage of OXlde. present.

We haverfoundthat ifthe atomization of such metal is carried on in anon-oxidizing or in a reducing atmosphere, the production or an oxidecoating on'the atomized particles may be reduced to a desired extent,the amount of oxide thus produced being substantially limited to theamount. of oxygen which the particles pick up solely from ,the waterspray. The amount of oxide coating thusproduced onsuch atomizedparticles will be so small that the oxygen content of a given mass ofparticles may be as low as approximately 0.06%, and rarely if ever, over0.5%. particles do not provide an oxygen inclusion in a mass of suchparticles greater than the percentage last stated, a satisfactory bondbetween the various particles, and between such particles and the steelstrip may be obtained in a sintering As long as the oxide coatings onsuch furnace without the necessity of further reducing the oxygencontent of the mass of powdered metal, and therefore the speed of thesintering operations may be substantially doubled over that whereconventionally formed atomized metal is employed as a powdered layer inthe manufacture of bearings or the like.

However, the atomization of such molten metal must not only be carriedon in a non-oxidizing or in a reducing atmosphere to obtain the desiredresults, but in order to be commercially practical, the operation mustbe such that excessive amounts of these non-oxidizing or reducing gasesare not used up in the process. This is accomplished in accordance withthe present invention by carrying on the atomizing operation within aspace substantially sealed against the admission of air into it, whichspace may be made a relatively small size and from which air has beendis placed by a non-oxidizing or a reducing gas,

small amounts of which are preferably continuously supplied thereto soas to prevent contamination of the gas by air. As a result, the onlyoxide coating which maybe found on the particles atomized will be causedsubstantially solely from the oxygen drawn by such particles when inmolten condition from the water employed in the atomization step, theamount of oxide formed thus being kept at a minimum.

It will be appreciated that the form of the apparatus to carry out themethod of thepresent invention may vary considerably in accordance withthe desires of the particular designer without any particular differencein result as long as the essential steps of the invention are followed.The apparatus shown in the accompanying drawing illustrate one form ofsuch apparatus which has been found satisfactory in the carrying out ofthe present method.

Referring now to the accompanying drawings, it will be noted that theapparatus comprises generally a tank or container in in one end of whichand adjacent the top thereof is positioned one or more nozzles, hereshown for the purpose of illustration as a single nozzle l2, arranged todirect a stream or spray of water therefrom preferably lengthwise of thetank as shown. It will be understood that the tank or container iseither closed or is otherwise sealed against the leakage of airthereinto. The nozzle I2 is connected by a pipe such as M with asuitable source of water under pressure, such as the pump l6.Preferably, the pipe [4 projects into the container lil through acoverplate or manhole cover 18 r emovably secured and sealed to thecorresponding end face of the tank or container it over the hole 20formed therein by means of bolts or screws such as 22.

Means are also provided for introducing a suitable reducing ornon-oxidizing gas such as nitrogen, hydrogen, helium, illuminating gaseither in its natural or cracked state, or the like, into the tank orcontainer Ill, and this may be done in any suitable manner and beobtained from any suitable source. In the drawings, such gas is obtainedfrom a conventional pressure bottle 24 from which it is fed to the tankthrough a conventional reducing valve or the like 26. In Fig. 1, onetube 28 is shown as extending from the reducing valve 26 through thecoverplate [8, to which it is sealed, into the interior of the tank orcontainer I 0 where it connects with a cross pipe. 30 disposed with itsaxis vertical and its opposite ends open for the escape of such gas intothe interior of the tank or container Ill.

Either one or both of these two means for intro ducing the nonoxidizingor reducing gases into thetankor container it may be employed, or anyother suitable means for producing an equivalent result may be employedin place thereof.

The molten metal which is to be atomized is introduced into the tank orcontainer i'il preferably in the form of one or more relatively finestreams which are discharged into the stream or spray 34 of waterissuing from the nozzle l2. While any suitable means may be provided foreffecting this result, the apparatus shown provides the followingdescribed means, as disclosed in Fig. 1. The upper wall of the tank orcontainer it is provided with a relatively short open ended cylindricaltube 36 which projects vertically through such wall and is rigidly fixedand sealed thereto as by Welding or the like. The lowerend of the tube33 terminates in vertically spaced relation above the stream or spray34, preferably a substantial distance from the nozzle l2 A suitablecrucible 38 is removably received,

preferably in more or less fitted relation,in the upper end of the tube3%. The bottom wall of the crucible 38 is provided with one or more fineholes 50 through which molten metal such as 42 introduced into thecrucible 33, as for instance from a ladle such as is, may flow in theform of f ne streams tie into stream or spray 3d. The stream orspray 35may be unconfined below the tube 38 where the molten metal is introducedinto it. On the other hand, if desired, the stream orspray 3 at thepoint where the molten metal is introduced into it may be confinedwithin an open ended tube :28, as shown in Fig. l, secured to the lowerend of the tube 36 and into which thetube 35 opens. Where the tube 48 isnot employed, then it may be desirable to provide a Window such as 50directly over the stream or spray 3d on the downstream side of the tube36 so as to enable the character of the stream or spray 34 to beVisually inspected. The window 50 is,-of course, sealed at its marginsto the tank or container in any suitable manner.

In order to permit the escape of air and gas from the tank or container,an inverted U- shaped tube 52 is provided at the rear end thereof withone leg thereof projectin through the upper wall of the tank as shown inFig. 1. Preferably, the other leg of the U is projected into a body ofwater such as 5 carried in an open top container such as 55 so as toprovide a water seal for preventing the leakage of air back into thetank or container iii. The rear wall of the tank or container H] islikewise provided with an overflow pipe 58 and, like the pipe 52, inorder to prevent leakage of air through into the tank or container lo,the pipe 58 is preferably provided with a downwardly extending endportion 60 which may be submerged in a body of water 62 in an open topcontainer 6t In this connection, it will be appreciated that the waterintroduced as the stream or spray 35 will fall to the bottom of thetank, and the pipe 58 serves as an overflow for such water and as ameans for maintaining a constant level ofwater in the bottom of the tankor, container I'll. Preferably, a drainage pipe 65 is .provided leadinginto the bottom v,

of-the tank, shown at the rear end thereof Fig. 1, and provided with ashut-off valve 68; so that the tank may be drained of water whennecessary or desirable. Additionally, the rear end of the tank orcontainer I0 is preferably provided with a hole it of sufficient size topermit a workman to crawl therethrough to the interior of the tank orcontainer Ill and this opening is normally closed and sealed by means ofa removable cover 12.

V The apparatus thus far described is sufficient, in the broader aspectsof the invention, for accomplishing thebroad purposes of the presentinvention, and in such case, its operation is as follows: The crucible38 is initially removed and,

thetop ofthe tube 36 closed, preferably in a more or less loose mannerso as to permit the escape of air upwardly therethrough under thepressure of the non-oxidizing or reducing gas employed.

The containers 56 and M are filled with liquid. Reducing ornon-oxidizing gas is then introduced intothe tank or container in fromthe bottle 24, either through the pipe 28, the pipe 32, or both, and isallowed to discharge into the tank or container H] at asufficient rateof flow and for a sufficient length of time to insure the bulk of theair being expelled or flushed therefrom, after.

i which the rate of flow is reduced to a point more fully explainedlater. Instead of expelling the air in this manner the overflow pipe 58may be closed and the tank or container H] be filled with water to expelor flush out the'air, the'pipe 58 thereafter being opened and anon-oxidizing or reducing gas employed to replace the water above thepipe 58 which then drains out. Insuch' case a relatively low rate offlow of the gas is established once the water in the tank l0 has reachedits normal level. Thereupon, water is'supplied to the nozzle i2 to formthe stream or spray -34, whereupon the crucible 38 may be introducedinto the upper end of the tube 36 and molten metal introduced into thecrucible so-that it will be discharged in the small or fine streams 46into the stream or spray 34. The fine streams of molten metalin beingengaged by the stream of the tank as a finely divided loose powder or asextremely small particles. The water. em-

ployed in producing the stream or spray is pref erablyunder a relativelyhigh pressure so asto enhance the breaking up of the fine streams 46' ofmolten metal into extremely fine particles. A water pressure of poundsper square inch has been found suitable. During the above describedoperation, the supply of non-oxidizing or reducing gas from the bottleas into the tank or container lfi-is continued, but only at a relativelysmall rate. All that is necessary is that a sufficient amount of anon-oxidizing or reducing gas be introduced into the tank of containerill to maintain the pressure therein slightly above atmosphericpressureso as to prevent any air on the outside of the tank or containerfrom finding its way into the tank or container through any cracks orapertures that'may not otherwise be sealed. However, the tankorcontainer It) may readily be sealed sufficiently completely so thatuntil a desirable amount of metal has been ghosts atomized anddeposited'in the bottom of the tank, upon which the flow of metal may bestopped, thegas and water turned off, valve 68 opened so as to drainthe'tank or containenand then the closure 12 removed and the atomizedmetal scraped or otherwise removed from the bottom of the tank throughthe opening 10. Where necessary or desirable, such atomized metal maythen be graded to different sizes adaptable for different uses. Inactual practice it is, of course, usually desirable to proyld features,other than those above-described as @sential, for enhancing theefficiency of the apparatus, to permit continuous operation'and forother reasons. For instance, it has been found that if one or morescreens such as '|4, suitably supported on the interior of the tank orcontainer ID, are provided in the path of flow of the stream or spray34, it will act to dissipate the force of the stream 34 and aid incutting down the turbulence imparted to the gas in the tank In by thestream 34. It also aids in preventing the water of the stream 34 fromsplashing back from the bailies hereinafter described, or whichotherwise might be picked up by the turbulent gas, from hittin thebottom of the cru cible 38 and freezing the metal 42 at the openings 40.Additionally, it is desirable, under some circumstances at least, toprovide some means whereby an initial separation of the particles intodifferent sizes may be accomplished in the tank or container l0. I

For the last described purpose, the bottom of the tank or container land over the rearward portion thereof may be provided with a pluralityof transverse troughs, which may be of any number desired but shown inthe drawings by way of illustration as three, namely 16, 18 and 80, withan upwardly projecting baflle or wall such as 82 between each, thebaflles 82 terminating below the level of the water within the tank orcontainer I8. When such an arrangement is employed, then some-means suchas the downwardly extending substantially imperforate baflle 84 ispreferably provided rearwardly. of the screen 14 but adjacent theforward'edge of the forward trough 16 so as to prevent the particles ofmetal in' the stream or spray 34 which pass through the screen 14 frombeing carried thereby beyond the first trough. In such cases, it is alsodesirable to provide a bafile 82 along the forward edge of the forwardtrough 16, as shown in Fig. 1, and then introduce a rearwardly directedstream of water along the bottom of the tank or container H] from theforward end thereof, as by means of the pipe 86, so as to carry anyparticles that may be dropped forwardly of the forward bafile 82 overthe top thereof. To facilitate this action, a curved sheet metal membersuch as 88, serving as a fillet, may be provided at the junction of thebottom wall forwardly of the forward baffle 82 and such forward baflle82, as brought out in Fi 1.

" With the abovedescribed construction the atomized metal which hits thebaffle 84 is directed downwardly into the body of water in the bottompart of the tank. This body of water which is made up by the water fromthe stream or spray 34 and from that introduced to the pipe 86, createsa current of water. which is continuously flowing from the front of thetank or container Hi to the rear thereof. The atomized particles ofmetal are ordinarily small enough to be capable of being picked up bythe flow of water and carried along with it, and any particles that aredeposited forwardly of the forward bafile 82 are forcefully washed bythe stream from the pipe 86 over such forward baffle 82. The particlesare thus firstpresented to the space between the first two bafiles 82 atthe forward and rearward edges, respectively, of the forward trough 1'6,and at this point the heavier particles will tend to drop into thetrough 76. The lighter particles will be carried by the stream of waterover the center baflle 82 to the space between the center bafile 82 andthe rear baflie 82 where the heavier of the remaining particles willtend to drop out and be deposited in the bottom of the trough 18. Thoseparticles still remaining in the flowing body of water will be carriedover the rear baffle 82 and into the trough 80, the latter thereforeserving to collect all particles which are not deposited in the troughsI6 and 18.

Some of the lighter particles may also be deposited out in the troughs16 and 18, that is particles of a smaller size than desirably separatedout in these troughs. To aid in preventing such occurrence it ispreferable to provide some means for agitating the water in the bottomof the troughs l6 and 18 so that any particles smaller than intended tobe deposited therein will be washed up into the moving body of water andbe carried on to their proper places of deposit. One means ofaccomplishing this last effect is to provide a transverse water headersuch as 88 adjacent each trough l6 and I8 and to connect each suchheader by a plurality of pipes such as 92 with a similar number ofnozzles 94, projecting through the bottom forward wall of the troughs i8and I8 and directed more or less in parallelism of the rear walls ofsuch troughs. The nozzles 94 for each trough l6 and 18 are preferablyarranged in equally spaced relation with respect to each other over thelength of such troughs, as brought out in Fig. 3, so that the waterprojected through the nozzles 94 from the headers will tend tocontinually agitate the mass of particles in the bottom'of the troughand thus cause the lighter ones thereof to be carried up and returned tothe body of water flowing along the bottom of the tank from the forwardend thereof to the rearward end thereof. In this manner, a moreeffective separation of the. various size particles is possible. 7

In order to enhance the effectiveness of the above-described separationmechanism, it may be preferable in some cases to extend baflles such as96 downwardly in the tank with the lower ends thereof projectingdownwardly below the top of the baflies 82 and centrally of each of thetroughs 16, 18 and 80. This produces the effect of a maze through whichthe body of water flowing from one end of the tank to the other end mustpass and accentuates the tendency of gravity in discharging theparticles from the streaminto the various troughs. The baflie 84 inparticular is preferably extended to the top of the tank so as toconfine turbulent currents of the gas in the tank or container 10resulting from the force of the stream or spray 34 thereon to theforwardportion of the tank or container l0.

In such case, of course, it is preferable to provide the bailies 96aswell as the baffle 84 with openings such as 88 adjacent their upperends to aid in insuring complete elimination of the air in the, tank orcontainer in when the air is flushed from the tank at the beginning ofeach cycle of operation of the apparatus.

Any suitable means may be provided for periodically or continuouslyremoving the deposits of atomized powder from the bottoms of the varioustroughs 16, I8 and 80, and the means hereinafter described and shown inthe drawings is illustrative of one way in which this may beaccomplished. In the particular form of appara tus shown and as broughtout in Figs. 2 and 3, the tank or container It] is formed with asemicylindrical upper portion, with vertical sides and a horizontalbottom wall. At each side of the tank or container I and over the lengthof the troughs I6, I8 and B0 is a trough I00, each of which has a sidewall I02 in outwardly spaced and parallel relation with respect to theside walls of the tank or container I9 and the bottom wall I04 of whichis on a level of the bottoms of the troughs I6, I8 and 80. The sidewalls of the tank or container I0 over the lengths of the troughs I09are extended down to the bottom wall IM, and these are cut out in linewith both ends of each of the troughs 19, I8 and 00 so that thesetroughs open fully at each end into the troughs l00. End walls I90 areprovided for each end of each trough I00, and partition walls I08 areprovided therein intermediate each adjacent pair of troughs Iii, I8 and80 so that each trough I00 is divided up longitudinally into as manypockets as there are troughs I5, I8 and 80, each pocket being opened toits corresponding trough It, II; or 00 and being sealed from the othersthereof. Theside walls I02 are of sufiicient height to extend above thelevel of the water in the tank or container I9 and to form a water sealfor the openings between the ends of the various troughs I5, I8 and 80and the outer troughs I00, thus preventing the entrance of air at thesepoints during operation.

In the construction shown, an axially movable rod I I0, as best broughtout in Fig. 2, is projected centrally and lengthwise through each trough15, I8 and 80, and the opposite ends of each rod I50 project through theopposite side walls I02 and are preferably suitably sealed againstleakage therein. Between the side walls of. each trough, a scraper bladeI I2 is fixed to each rod I 10. The scraper blades H2 extendtransversely of the length of the troughs I9, I6 and 80 and each is of ashape complementary to the cross sectional shape of the correspondingtrough, and preferably bears against the converging bottom walls of thecorresponding trough. It will be appreciated that when rods IIO areaxially reciprocated either manually or mechanically, they will becaused to travel longitudinally of their respective troughs I6, 18 and80 and in being reciprocated with scrape any deposit of atomized metalin such troughs out into the pockets I00, from which it may be readilymanually or otherwise removed. Thus with the apparatus as thus fullydescribed and shown, continuous operation of the apparatus may becarried on.

To permit complete draining of the tank and troughs, it is necessary, inthe construction shown,

, aration to provide drainage pipes II4 on the level of the bottom ofeach trough I6, 18 and and in communication therewith, each of the pipesbeing provided with a shut-off valve I I6.

Having thus described our invention what we claim by Letters Patent is:

1. In the atomization of metal, the steps of flushing air from aconfined space and replacing such air with a non-oxidizing gas,maintaining a pressure within said space slightly greater thanatmospheric by the continued introduction into said space of anon-oxidizing gas, introducing a stream of water flowing at a relativelyhigh velocity into said space, introducing a relatively fine stream ofmolten metal into said high velocity stream of water within said space,partially obstructing the flow of said high velocity stream of waterafter the introduction of said molten metal thereto whereby to dissipatethe force ofsaid stream of water, creating a unidirectional flow ofwater in the lower portion of said space for receiving particles of saidmolten metal broken up and solidified by said high velocity stream ofwater, and efiecting gravitational sepof said particles into a pluralityof different sizes under the effects of said unidirectional flow of saidwater.

2. In the atomization of a metal alloy of a type in which copper andlead are the principal elements, the steps of driving air out of asubstantially confined space and replacing such air with a non-oxidizingas, introducing a nonoxidizing gas into such space to maintain anonoxidizing atmosphere therein, continuously projecting a high velocitystream of water into said space, substantially continuously feeding arelatively fine stream of said alloy in molten condition into said highvelocity stream of water whereby to cause said molten alloy to be brokenup into fine particles and solidified as such, providing a moving bodyof water in the said space below said high velocity stream of water toreceive said water and said particles and carry said particles adistance varying with the weight thereof, and removing said particlesfrom said space while maintaining a non-oxidizing atmosphere therein.

GORDON J. LE BRASSE. HAROLD E. FRANCIS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,156,079 Holley Oct. 12, 19151,709,365 Newsom Apr. 16, 1929 2,159,433 Ervin May 23, 1939 2,255,206Duncan Sept. 9, 1941 2,384,892 Comstock Sept. 18, 1945 Certificate ofCorrection Patent No. 2,460,992. 2 February 8, 1949.

GORDON J. LEBRASSE ET AL.

It is hereby certified that errors appear in the printed specificationof the above numbered patent requiring correction as follows:

Column 2, line 46, for Tin 5 to 12 read Tin 2 to 12; column 9, line 55,for the Word wit read will;

and that the said Letters Patent should be read with these correctionstherein that the same may conform to the record of the case in thePatent Office.

Signed and sealed this 5th day of July, A. D. 1949.

[SEAL] THOMAS F. MURPHY,

Assistant Gommz'ssz'oner of Patents.

